Big quakes no more likely than in past: study

Dec 19, 2011
A homeless survivor walks by a collapsed building after an earthquake in Ercis, Turkey, in October 2011. Massive earthquakes are no more likely today than they were a century ago, despite an apparent rise in recent years of the devastating temblors, US researchers said on Monday.

Massive earthquakes are no more likely today than they were a century ago, despite an apparent rise of the devastating temblors in recent years, US researchers said on Monday.

The deadly 9.0 earthquake this year in Japan, an 8.8 in Chile last year and the 2004 Sumatra-Andaman earthquake that registered 9.0 on the moment magnitude scale have raised alarm in some science and media circles that such events may be linked.

But researchers at the University of California went back over the world's earthquake records dating back to 1900 and found over time there was no statistically significant rise in the number of big quakes 7.0 and higher.

"One has to be careful, because humans have a tendency to see patterns in random sequences," lead author Peter Shearer of the UC Berkeley Department of Statistics told AFP.

"So what we wanted to do here was apply to see whether you could say it wasn't just a random sequence of events," said Shearer, whose study appears in the .

"Those tests showed that you can't say that it is not random; that is, there is not a statistically significant degree of the clustering of events," he said.

Even though there is "a disproportionate number of very large 8.5 earthquakes between 1950 and 1965," there were uncommonly fewer of these during a much longer period afterward from 1965 to 2004.

And although there has been a more frequent rate of 8.0 and larger quakes since 2004, with the last five years in particular at a record high, "there have been rates nearly as high in the past," said the study.

The researchers also looked for any clues from the Earth's crust that could explain why or how big quakes might be linked.

"And the conclusion was no, there isn't a likely physical cause that would link for example a large in South America to one in Japan," Shearer told AFP.

"The events are just too far away for it to be very likely that there is a physical link between them."

Taken together, the two approaches "suggest that the global risk of large earthquakes is no higher today than it has been in the past," concluded the study.

The findings are in line with a study in Nature Geoscience earlier this year that found the regional hazard of larger earthquakes is increased after a main shock, but the global hazard is not.

That study countered an earlier 2009 paper in Nature that suggested seismic waves might have an effect on distant fault lines, potentially increasing the risk of earthquakes far away.

Explore further: New study confirms water vapor as global warming amplifier

More information: The global risk of big earthquakes has not recently increased, by Peter M. Shearer and Philip B. Stark, PNAS, 2011.

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User comments : 6

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Husky
3 / 5 (4) Dec 19, 2011
with the present populationsize, we are bound to find ourselves living in disasterprone areas that used to be uninhabitat or had a sparse population and no internet to upload the movie to youtube.
Callippo
2.3 / 5 (3) Dec 19, 2011
In these studies the intensity of geovolcanic activity increases instead. http://nujournal....Rise.pdf http://www.market...9983.htm I tend to believe in these trends, as it supports my theory about geothermal origin of global warming. After all, the switching of geomagnetic poles is connected to circulation of matter inside of Earth core and if it reverses, it must have some impact to the Earth mantle.
verkle
1 / 5 (2) Dec 19, 2011
Callippo, the article that you point to is in direct contradiction to the point of this article. It would be intereseting to see the same energy graph of earthquakes for years prior to 1974 as well.
Callippo
1 / 5 (1) Dec 19, 2011
Callippo, the article that you point to is in direct contradiction to the point of this article. It would be interesting to see the same energy graph of earthquakes for years prior to 1974 as well.

It's difficult to say, because the more intensive geovolcanic activity could actually lead to weaker, but much faster earthquakes, because the friction tension in Earth mantle is released more often and as such in more reversible way. The total energy of quakes is what counts here. The less intensive earthquakes were missed easily at the beginning of the last century because of lack of dense seismograph network and central evidence of quakes. The less dense network of seismographs in history could lead to the detection of weaker signal, because the centers of quakes were more distant from seismographs in average.
Shifty0x88
5 / 5 (1) Dec 19, 2011
So the fact that there was a east-coast quake, though it was minor here in New Jersey, is what coincidence? Or just the result of a build up that would have been at least 24 years in the making? HHhhhmmmm
MarkyMark
not rated yet Dec 20, 2011
So the fact that there was a east-coast quake, though it was minor here in New Jersey, is what coincidence? Or just the result of a build up that would have been at least 24 years in the making? HHhhhmmmm

Yes it probably was coincidence.